Volume 3, Number 9 - September 1998

Journal of the Home Metal Shop Club of Houston, Texas

President - George Carlson, V. Pres.- J.D. Wise, Treasurer - Gordon Lawson
Secretary - Keith Mitchell, Editor - Robert Travers , Email rtravers@enron.com

Notes from the President

What? You've been a little tied up lately and haven't made been able to spend time in the shop? Homurous photo stolen from a bookThe weather is getting better, so the shop should be habitable, the kids are off to school, and vacations are over; so get to work!

The project for last month was "Something for the Yard". Dean brought in a device for pulling up fence posts. It was well designed. I hope he enjoys using it. For September the challenge is, "Clamps and Workholders". Build some new widgets for clamping or positioning work and bring them in.

Our presentation schedule has been changed up a bit but I think you will still enjoy what is in the works. John Oder has volunteered to do a demonstration on scraping and the generation of precision surfaces for the September meeting. (If he doesn't get shipped off to Ohio on business) John has many years of experience in this area. I am really looking forward to his demo.

In October we will be doing a special program on ideas for shop made Christmas gifts. We need a volunteer or two to gather up as many ideas as possible and organize them for the group. Things like toys, games, and decorative items are popular and very special if they come from your shop.

Don't forget about the upcoming Swap Meet. It will be located in the parking lot of Rutland Tool at 8:00 AM on Saturday the 24th of October. Bring your goodies and some cash.

The next meeting day is September 19th. Don't forget the business meeting at Barbecue Inn at 11:30, everyone is invited.


Minutes of Meeting August 15, 1998

by Keith Mitchell

Swap Meet - Rutland Tool has agreed to host the Second Annual Swap Meet. Time and place are October 24 at 8:00 am in the Rutland Tool parking lot. George Edwards is coordinating this event. The First Annual Swap Meet was quite a success. It's an opportunity to unload all of those treasures, which were so necessary at the time, but you have since forgotten why. Rutland supplies lunch followed by a combat auction of orphaned items by Rutland. You probably want to start putting away some mad money now for this event.

Monthly Challenge - John Lily brought the only entry to the monthly challenge. John brought a fixture for a floor jack to jack fence post out of the ground. Having removed about 200 of these one nice August day, I can appreciate the usefulness of this item. Next month's challenge is to make some type of workholding fixture or clamping device.

Phase Converters - George Carlson made a presentation on Phase Converters. We all learned that there are many explanations of why an electric motor works. Both static and rotary phase converters were discussed along with the advantages and disadvantages of each. Both theory and practice were presented. Thanks to George for an excellent presentation.

Newsletter Articles - Our newsletter editor, Robert Travers, sent an urgent request for newsletter articles. It's not necessary to be a literary giant to prepare a newsletter article! If you can submit the article handwritten with a few hand drawn sketches, we can develop a credible newsletter article. What's lacking at this point is ideas!

Shop Hints - A new section has been added to the newsletter for shop hints. We have all found better ways of doing things, which we can share with the other members.

Bob Arnold - As many of you are aware Bob Arnold has been undergoing treatment for a brain tumor. He became ill during the last meeting and had to leave early. We all hope Bob is feeling better.

John Korman brought in the low-temperature Stirling engine he has been working on. It will very nearly run off the heat of a hand. John's goal is to produce an engine with that level of sensitivity. Not a simple task.

Properties of Metal

By Robert Travers

To work with metal you first need to understand it. different alloys have different properties. Some metals are strong, some are brittle, some are easily corroded, some are corrosion resistant, some are expensive, some are less expensive. Here are the engineering properties of some of the more common metals we encounter.

Cast Iron - comes in various types. Not an engineered metal, it's chief advantages are it's cheap, easy to cast and doesn't corrode easily.

Steel - generally divided into three categories, low, medium and high carbon steel. The more carbon, the harder it will become with heat treating. It can also be alloyed with other materials, usually chromium, molybdenum, silicon and nickel.

Stainless Steels - Alloy steel containing Chromium, nickel and molybdenum. Resists corrosion and can be polished to a high gloss. Keeps it's strength even at elevated temperatures. Very strong when heat treated, and very expensive.

Free machining steels -Made by mixing steel with small amounts of sulfur and lead or sulfur and manganese. Machines easily and makes very small chips, but not as strong as other steels.

Electrical steels - silicon steels reduce eddy currents and heat loss in electric motors and generators. Cobalt alloy steels make very strong permanent magnets.

Tool steels - high carbon alloys selected for toughness and wear resistance.

Coding - Steel is designated by codes. Some examples:

1xxx - carbon steel

2xxx - steel with nickel

3xxx - steel with nickel chromium

40xx & 44xx - steel with molybdenum

41xx - steel with chromium and molybdenum

43xx - steel with nickel, chromium and molybdenum

The last two digits of the code indicate the steels approximate carbon content in hundredths of one percent. For example 1020 steel would be plain carbon steel with 0.20 percent carbon content.

Aluminum - by itself is usually too soft to be machined, but when alloyed with other materials, it becomes very easy to machine and has some very useful properties.

Coding - like steel, aluminum manufacturers use codes to identify different aluminum alloys.

1xxx - pure aluminum

2xxx - aluminum with copper

3xxx - aluminum with manganese

4xxx - aluminum with silicon

5xxx - aluminum with magnesium

6xxx - aluminum with magnesium and silicon

7xxx - aluminum with zinc

Some examples of aluminum alloys are:

2024 - high strength to weight ratio

3003 - 20 percent stronger than pure aluminum, easy to form

6061 - less expensive than the others, and welds easier

Warning - when buying scrap aluminum, be careful. Aluminum and Magnesium are both lightweight grey/silver colored metals, but magnesium burns at high temperatures, which makes it less than ideal for machining operations.

Copper - is soft and difficult to machine. Tools must be very sharp or you will be left with a rough and ragged finish. It has high thermal and electrical conductivity, resists corrosion and can be polished to a brilliant luster, but it's too soft in it's pure state to be used for structural purposes.

Brass - is an alloy of copper and zinc. It is difficult to machine because it clogs the teeth of saws and files and requires a very sharp tool ground at a different angle from that used on steel. Add a little tin and it becomes Admiralty brass, very resistant to corrosion. Adding 2 to 3 percent lead makes the brass easier to machine. 50/50 copper zinc is used for brazing, and makes very strong joints.

Bronze - is basically an alloy of copper and tin. Strength increases with tin content up to 20 percent. Beyond 20 percent the bronze becomes brittle. Phosphor bronze ( 1 to 11 percent tin, less than 1 percent phosphorus) is hard, with excellent wearing qualities, and is commonly used for pump parts, gears and bearings. Aluminum bronze (6-12 percent Aluminum and 2-5 percent iron), Silicon bronze (4 percent silicon and 1.5 percent tin), and Copper-Beryllium alloys can be as hard as steel and have great strength, but they are also very expensive.

Magnesium - the lightest metal. Good casting and machining properties, but there is a problem. Magnesium chips and powder burns at temperatures above 425 degC (800 degF). This makes it a difficult material to use in the average home shop. If you machine any magnesium, make sure to keep it cool, and dispose of all chips in a safe manner. Don't leave them in the trash bin at your shop.

Plastics - although plastics aren't metal, we sometimes have a use for them. Plastics come in two major groups, thermosetting and thermoplastic. Thermosetting materials can be used once, thermoplastic materials can be melted down and reused over and over again. Plastics are lightweight, have high electrical and thermal resistivity, come in an almost unlimited range of colors, are easily formed and can easily be given an excellent surface finish. Their primary disadvantage is their lack of strength. Most plastic products are formed by casting, and molding, but most can be machined. You must remember certain facts however;

1. Plastics are poor heat conductors, so the heat of machining operations will not be carried away by the chips. Tools will run hot and may fail more rapidly than when cutting metal.

2. Thermoplastic materials tend to soften under the heat of machining operations, binding and clogging the tools. Thermosetting materials don't have this problem. Cutting tools should be kept very sharp. Straight flute drills work best for drilling. Saws and milling cutters should be run at high speed to improve cooling, but keep the feed rate low.

3. Coolants may discolor the material. Water, soluble oil in water and sodium silicate in water are good coolants.

4. Some plastics, fiberglass for example, are very abrasive. Tool wear can be very high when machining some plastics.

Nylon - good abrasion resistance and toughness. Used as bearings with little lubrication.

ABS - low weight, good strength, very tough.

Polycarbonates - high strength and outstanding toughness

Rubbber - parts can be cast. Some materials coat objects that are dipped in them.